The mdm-2 oncogene encodes a zinc finger protein composed of 491 amino acid residues. The amino terminal domain of mdm-2 (residues 16 - 120) bind to an inactivate the p53 transcription factor activity. Residues 200 - 300 in the mdm-2 protein binds the L5 ribosomal protein and 5SRNA while the zinc finger domain is localized between residues 300 - 491. Experiments have been designed to test whether the mdm-2 oncogene can transform cells when the target cells do not have the p53 gene or fail to produce the p53 protein. If overexpression of the mdm-2 protein in a cell with no p53 can enhance the tumorigenic potential of the cells, we will map the mdm-2 domains responsible for this phenotype. Experiments been formulated to identify putative genes regulated by mdm-2 in a cell, and a yeast two hybrid system is being utilized to identify proteins that can bind to and alter mdm-2 activities. The RNA-SELEX procedure is being utilized to determine if specific RNA sequences or structures will bind to mdm-2 protein and if so, to which domain of the protein. Cell lines in some complementation groups from Cockayne's syndrome (Cs-B) and Xeroderma pigmentosum (XP-A) will induce p53 in response to DNA damage, but fail to induce high levels of mdm-2 (a p53 responsive gene). Experiments are planned to determine the nature of this defect.